Poster: Enzymology

Abs # 228: Identification of knock-out mutants for three starch branching enzyme isoforms in Arabidopsis thaliana

Presenter:	Blauth, Susan L, susan_blauth@redlands.edu
Authors	Blauth, Susan L (A)   Purteymoor, Sheila  (A)   Newkirk, Cristin  (A)   Plumlee, Lora  (A)   Duenas, Janice  (A)
Affiliations:	(A): University of Redlands

Starch branching enzymes (SBE) break the a-1,4 linkage of starch, reattaching the released glucan chain to another chain by an a-1,6 bond. In this way SBEs interact with other enzymes to determine starch structure which subsequently determines the physical properties of starch. SBE isoforms fall into two classes, type I or type II, based upon their amino acid sequence and biochemical properties. Two cDNA sequences have been isolated from Arabidopsis and named Sbe2.1 and Sbe2.2 based on their high homology to the maize sequence encoding type II SBEIIb. A third sequence with high homology to Sbe 2.1 and Sbe 2.2 has been identified during analysis of ESTs through the Arabidopsis genome project. In order to examine the function of the SBE isoforms, T-DNA insertion mutants were selected from the Salk Institute Genomic Analysis Laboratory's sequence-indexed collection for each of the three Sbe homologous sequences. Homozygous mutants for each of the three sequences were identified using PCR, and the position of the T-DNA insertion within each sequence was verified by DNA sequencing of the amplification product. Characterization of these mutants will be presented.